Ge/Ay133 What can meteorites tell us about the early S.S.?

Ge/Ay133

What can meteorites tell us about the early S.S.?

What kind of meteorites are there?

The systematic collection of meteorites from Antarctica has dramatically increased the number of samples available.

StonyIron

Chondrite types and sample chondrules:

Extinct radionuclines give assembled time scales of 5-50 Myr. When is t=0?

Absolute dating error bars getting down to ~1 Myr!

An amazing variety of organics are found in chondrite matrices, esp. a wide variety of aliphatic and aromatic hydrocarbons, carboxylic acids, amino acids, purines, pyrimidines, and sugars. Synthesis?

From whence the complex nebular organics?

D values are large, structural diversity complete. Supposedly formed by aqueous alteration of ISM precursors on parent bodies, but organic and silicate aqueous signatures are contradictory. Can the organics be made in the disk? The oxygen fugacity is critical.

L excess in Murray, Murchison meteorites (isovaline shown)?

How might you generate such an excess?

Geochem. Cosmochim. Acta 64, 329(2000)

Achnodrites:

No chondrules, “planetary” processes. Can find examples from the Moon & Mars!

Thin sections appear similar to terrestrial basalts.

Johnstown Achondrite

Iron Meteorites: Widmanstätten crystallization patterns indicate slow cooling.

These irons and pallasites likely originate in the cores or core-mantle boundaries of differentiated bodies.

Next time: Core formation & terrestrial planets.